The present invention relates to a measuring method and a measuring instrument to measure a multiple number of points periodically or continuously over time.
For the purpose of observing the sinking of ground, of observing landslide, of observing displacement of banks and walls of construction work such as a dam, of observing displacement of wall surface of a tunnel, measurement is performed periodically or continuously over time by using a measuring instrument on a multiple number of measuring points, which are set up in a measurement range.
For instance, in case where a tunnel is to be constructed to build underground railway, for the purpose of observing whether ceiling and wall surface of the tunnel constructed may not be displaced or not, a multiple number of prisms are installed on the ceiling and on the wall surface as targets, and positional displacement of all these prisms are measured one after another without operator intervention by using a measuring instrument (hereinafter, this is referred as “monitoring measurement”).
Because automatic sighting and distance measurement must be performed each time when distance measurement and angle measurement are to be carried out on each of the measuring points, in case there are a multiple number of measuring points, much time is required for a single monitoring measurement, and the time required for the monitoring measurement will be longer. Therefore, there has been an apprehension that a delay in discovering a change is caused when any change occurs on the measuring point.